Towed vehicles, such as trailers that are towed by towing vehicles (trucks or pickups) are commonly provided with electric wheel brakes. Typically, the braking force produced by the brakes is proportional to the electric current applied to the brakes. Electrically actuated brakes can be driven against the ground potential of the vehicle's power supply, which can be, for example, a battery. Thus, one end of each of the towed trailer's brakes is electrically connected to the trailer ground and the trailer ground is electrically connected to the towing vehicle ground. The other end of each of the trailer's brakes is electrically connected through a brake controller to the towing vehicle's power supply.
FIG. 1 is a diagram illustrating the structure of a conventional trailer 110 towed by a towing vehicle 120 such as a pickup or a truck. As shown in FIG. 1, the trailer 110 comprises a conventional sway controller 112, trailer brakes 114, and brake lights 118. The towing vehicle 120 comprises a brake controller 122, a brake switch 124, a battery 126, and brake lights 128. The brake controller 122 is electrically connected to the sway controller 112 through a wire 102. The brake switch 124 may be a brake pedal or a manual switch which is electrically connected to the brake controller 122 and the brake lights 118 and 128 through another wire 103. The battery 126 is electrically connected to the brake controller 122 and the sway controller 112 through a power wire 101 so as to provide power to the brake controller 122 and the sway controller 112 as well as the devices connected thereto. The sway controller 112 is also electrically connected to the trailer brakes 114 through the power wires 104.
When a driver in the towing vehicle triggers a brake action such as stepping on a brake pedal (not shown) or pressing a brake button (not shown), the brake switch is turned on and sends a brake signal to the brake controller 122 and the brake lights 118 and 128. According to FIG. 1, the brake controller 122 is located in the towing vehicle 120 for sending a desired controlling signal to the sway controller 112 through wire 102 responsive to the brake signal sent from the brake switch 124 through wire 103, so as to control the trailer brakes 114. Various brake controllers for controlling trailer brakes are known in the art.
As known to persons with ordinary skill in the art, a sway controller can be disposed either in a towing vehicle or in a trailer. However, a sway controller being disposed in a towing vehicle would have the following drawbacks. Firstly, since a sway detecting sensor is usually located in the sway controller, if the sway controller is disposed in the towing vehicle, the sway detecting sensor can only detect the sway of the towing vehicle, which is itself caused by the sway of the trailer connected to the towing vehicle and is relatively less noticeable than the sway of the actual trailer. Thus, the sensitivity of the sway detecting sensor and the ability of the sway detecting sensor to accurately determine the sway of the trailer would not be ideal. Consequently, the ability of the sway controller to control the sway of the trailer, which depends on the sensed sway, would not be ideal either. Secondly, there are already a number of trailer providers in the market that provide trailers with sway controllers incorporated therein, and the sway controllers in such trailers can usually be connected to the brake controller of a towing vehicle through an existing standard connector. In such a case, if the towing vehicle is also equipped with a sway controller, the towing vehicle would not be suitable for a connection with a trailer with a sway controller incorporated therein because (1) such a towing vehicle may be incompatible with the existing standard connector, (2) one of the two sway controllers may be redundant, or (3) the two sway controllers may be incompatible with each other.
FIG. 1 shows an example in which the conventional sway controller 112 is located in the trailer 110. The conventional sway controller 112 may include a gyro sensor or a gyroscope (not shown) and is configured to detect the sway of the trailer 110 via the gyro sensor and to stop or reduce the sway through engaging the trailer brakes 114. According to the operation of the conventional sway controller 112, when the driver triggers a braking action, the sway controller 112 must be instructed by the brake controller 122 and cannot work independently.
However, the conventional sway controller has several drawbacks. First of all, the conventional sway controller can only be instructed by the brake controller so as to control the trailer brakes, but cannot control the trailer brakes independently. Therefore, a towing vehicle towing the conventional trailer with the conventional sway controller must be equipped with a brake controller for controlling the trailer brakes. Furthermore, since the conventional sway controller must be instructed by the brake controller through wire 102, if the brake controller and/or wire 102 malfunction, the sway controller cannot engage the trailer brakes so as to slow down or stop the trailer, which may cause dangerous accidents.
In order to address the above-mentioned drawbacks, there is a need for an improved trailer brake control device, which can work independently or can detect whether the brake controller is functioning properly.